According to the United States Environmental Protection Agency, the United States generated approximately 34 million tons of food scraps in 2009. That's 22 tons or roughly 3 times the amount that was generated in 1960. That number continues to grow every year as the population continues to increase. In fact, while the average American generated only 120 lbs. of food scraps in 1960, that figure increased to 221 lbs. in 2009. At the rate of increase between 1960 and 2008, the amount of food scraps generated by Americans will grow to over 39 million tons by 2018.
Public and private sectors are facing increasing transportation and disposal costs for all discards, including food scraps. There is also increasing concern about the sustainability of current disposal practices, which are instigating investigations into more environmentally benign disposal options. Previous methods such as landfilling and incineration are being increasingly recognized as unsustainable.
Transporting food scraps to landfills contributes enormously to anthropogenic sources of greenhouse gases such as carbon dioxide and nitrogen and sulfur oxides as well as other general air pollutants such as particulate matter, volatile organic compounds, and carbon monoxide. Once land-filled, organic discards such as food scraps contribute to methane production, a greenhouse gas believed to be 20-70 times more effective at trapping heat in Earth's atmosphere than carbon dioxide. While some landfills are collecting the methane gas, most do not; it is simply vented to the atmosphere. In the U.S., this situation is further complicated by the rapidly approaching closure of many landfills.
Transporting food scraps to incinerators, or waste-to-energy facilities, contribute in the same manner to greenhouse gas emissions. The difference is that while no methane is emitted, other gases are. Additionally, food scraps have one of the lowest BTU values per pound. Compared to plastics, which range between 11,000 and 20,000 BTUs/lb.; rubber, which produces approximately 11,000 BTUs/lb.; newspaper, which produces 8,000 BTUs/lb.; cardboard, which produces 7,000 BTUs/lb.; food scraps produce only 2,600 BTUs/lb. Consequently, incinerator operators may be forced to supplement their fuel source with fossil fuels to maintain high burning temperatures if too much of their fuel is food scraps.
The benefits of aerobic digestion of organic discards are well documented. In fact, it is the planetary default for the recycling of organic matter. When systems designed by humans replicate these biological processes, it is known as composting and the end-product is known as compost. Commercial or industrial applications have often focused on outdoor windrowing technology. Problems associated with this option include odors, limitations on what may be composted (animal products are often excluded), time to produce the compost, and energy required. Recently, interest in aerobic in-vessel rotary drum technology (known by various different names, including rotary drum) has increased. This is because many of the concerns about windrowing are addressed. Because they are contained units, aerobic in-vessel systems dramatically reduce odor issues; remove limitations about what may be composted (animal products are acceptable), dramatically reduce the time to produce the compost, and require much less energy. It has also been suggested that “Harvesting food waste as a reusable resource is the next frontier in recycling.”
Despite such encouraging comments, the recycling of food scraps via composting has remained at about 2.5% of the total amount generated since 2000. Part of the explanation for this finding is that many of the existing aerobic in-vessel rotary drum digestion systems available to the mass market have not been value-engineered, do not include required safety features, and are aesthetically unpleasing.
In light of these and further disadvantages of prior art composting system and methods, including their relative complexity and other design shortcomings, it is clear that there remains a need for an improved composting system and method that overcomes one or more of the disadvantages of the prior art. It is clearer still that a composting system and method that provides a solution to each of the above-described advantages while demonstrating enhanced effectiveness and utility would represent a market advance in the art.